DETERMINING WELL EFFICIENCY BY MULTIPLE STEP-DRAWDOWN TESTS

Graphical solution of multiple step-drawdown test data permits an approximate determination of the two components of drawdown in a pumped well; that due to formation loss, and that due to well loss. This in turn permits an engineering estimate of the '"efficiency" of a well. An understanding of the various factors affecting well efficiency is important because savings in well design and construction and operation can be made by increasing the efficiency of a well and thus preventing much needless waste of materials and pumping energy. Data collected during step-drawdown tests of 32 screened wells tapping alluvial sediments in northern and western Iran are presented, together with data from 16 tests on 11 perforated and 3 screened wells in southeastern Washington State.